I am feeding my 5 month old GSD Fromm Large Breed Puppy. She seems to really like the food. She has been on it long enough to go through the large bag so it is not a newly introduced food. Her stools are firm when I take her out in the morning but when I take her out in the evening they can be very loose and sometimes runny. Is this normal? Sometimes they will be very loose, sometimes they will start firm and the end of the movement is loose.